The field of the present invention is an internal combustion engine and particularly an internal combustion engine having a single overhead camshaft.
Internal combustion engines may utilize overhead valves. In these engines each cylinder typically has an intake valve and an exhaust valve. The engine may utilize a single camshaft to operate both the intake and exhaust valve such as disclosed in U.S. Pat. Nos. 3,353,523, 3,306,271 and in FIG. 48 of U.S. Pat. No. 3,316,890. The engine may also utilize two camshafts, a first camshaft to operate the intake valve and a second camshaft to operate the exhaust valve such as disclosed in FIG. 47 of U.S. Pat. No. 3,316,890.
One camshaft centered between the valves can activate both the intake valve and the exhaust valve. But when the camshaft is centered it is difficult to position the engine spark plug axially in line with the cylinder axis. The use of two camshafts permits axially positioning of the spark plug but it requires a complex timing mechanism to drive the two camshafts from the crankshaft. The use of a second camshaft and associated timing mechanism also requires mounting space which increases the size of the engine, the weight of the engine and the cost of the engine.